A vehicular oil level detecting device is known wherein a detection level is set between an oil level at the time of turning on an ignition switch and an oil level at the time of starting an engine in view of the fact that the oil level in an oil reservoir is decreased at the time of the starting of the engine. In addition, an oil level switch is adapted to be operated when the oil level is less than or equal to the detection level mentioned above. The oil level switch is provided in the oil reservoir. See, for example, Japanese Utility Model Laid-open No. Hei 5-66523 (FIG. 4).
In the technique described in Japanese Utility Model Laid-open No. Hei 5-66523, when the oil level switch has already been operated (OFF position as defined in Japanese Utility Model Laid-open No. Hei 5-66523) at the time of turning on the ignition switch, an oil warning lamp is turned on.
However, the conventional vehicular oil level detecting device mentioned above has a problem such that when the oil level switch suffers an open position failure (i.e., the OFF position is always held), improper determination may be made in such a manner that the oil level is improperly determined to be normal in spite of the lack of oil in the oil reservoir.